/**
 *  cpu_c.c - init_stack is only implemented.
 *
 *  Copyright (C) 2008-2010  ZhangHu
 *  All rights reserved.
 *  E-MAIL: anmnmnly@gmail.com
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include "include/core.h"
#include "regdef.h"
#include "cpu.h"

/**
 * init_stack - Initialize task stack.
 * @pstk: Pointer to peak of stack.
 * @reg_cnt: Number of Registes that needed to initialized.
 * @return: Peak of stack.
 *
 * @notes: PC has been initialized, and it was set in the bottom of stask.
 */
void init_context(int32 *space)
{
    int32 *p = space;
    int32 i = 0;
    int32 reg_cnt = 17;
    int32 value[17] = {
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x1F, 0x1F
    };

    if(p == NULL ) {
        return;
    }

#if STACK == UP  /* Up Growth */
    for(i = 0; i < reg_cnt; i++) {
        *p++ = value[i];
    }
    p--;
    space[2] = (int32)p; // space[2] is SP.

#else   /* Down Growth */
    for(i = 0; i < reg_cnt; i++) {
        *p-- = value[i];
    }
    p++;
    p[15] = (int32)p;  // P[15] is SP.
#endif
}

